From the one-dimensional editing of its first twenty minutes, “Food, Inc.” could be another well intentioned but poorly played guerilla documentary from Robert Greenwald. So much of this intro is taken up by vague condemnations of agribusinesses, accompanied by obnoxious computer animation meant to convey their shadowy nastiness, that it threatens to waste away in the self-righteous vein of Greenwald’s screeds against Fox News and Wal-Mart.

But surprisingly, and thankfully, Greenwald had nothing to do with this documentary, and that becomes clear as it progressively improves. It’s actually the brainchild of two authors and long-time critics of the food industry, Eric Schlosser and Michael Pollan, and is directed by Robert Kennen, who is able to take a very rough beginning of disconnected snapshots and turn it into a satisfying and somewhat complete film in the spirit, though not the best, of the muckraking tradition.

What the documentary has to show is necessary viewing for anyone who eats just about anything at all. It exposes, like the books by its creators that act as source material, the horrible costs of our hyper-industrialized food industry, which are all too often hidden behind government subsidies and slick PR campaigns.

The Monsanto Corporation is one nebulous example. It is slowly reviving agricultural serfdom through a genetic monopoly on patented soybean strains, bringing small farmers under its legal tentacles. Kennen interviews some of these all-American farmers whose careers were ruined by one multi-national corporate giant, and their emotional wounds are still raw for the audience to see.

The Bush Administration, admittedly an easy target, is another example. By now no one will be surprised to know that they staffed federal regulatory agencies with former lobbyists for the industries they were meant to regulate. They then turned around and pointed their fingers at liberals when those agencies, the FDA and the USDA, failed to prevent bacterial outbreaks, as if the foregone conclusion of failure somehow proved the futility and inefficiency of regulation. This is enough to get up in arms about without having to see injustice in our own backyard, but Kennen also interviews a union organizer in Tar Heel, N.C., where the largest hog slaughtering plant in the world (owned by Smithfield Foods) is running through thousands of pigs and hundreds of low-paid workers every day. Their unfair labor practices have been under plenty of scrutiny recently, and Kennen, Pollan and Schlosser all insist that this inhuman business model is one link in a food chain that is killing people as fast as it’s killing the planet.

From a beginning that seems to be heading nowhere, Kennen fashions a little bit of cinematic agitprop that conveys this message admirably. At the rolling of the credits, “Food, Inc.” is too technically sloppy to be considered well-made, but still thoughtful enough to be a fair and heartfelt statement about the enormously important issue of unethical food production.